Your neighbor appears to be intentionally damaging your property, but it isn't clear from your question where the extended pipe of your neighbor's house goes. You may have a claim for nuisance. Take pictures and show them to an attorney who practices civil law and real estate. If the pipe is pointed straight at your property and you can show damage as a result, you may have a good claim. While everyone is entitled to the use of their own property, they cannot use it in such a manner as to cause a nuisance to another's property. Maybe suggest a pipe that disperses the water instead of directing it just toward your property.